France has become the first country to recognise the Libyan rebel leadership, the National Libyan Council (NLC), as the country's legitimate government.
But other members of the European Union held back, with a spokesman for the EU's foreign affairs chief warning against "rushing" into decisions.
In another development, the Gaddafi government said a captured Dutch helicopter crew was being handed over.
Nato chiefs have also been meeting in Brussels to discuss Libya.
Separately, a search was under way in Libya for a missing reporter for the UK's Guardian newspaper, Ghaith Abdul-Ahad.
The award-winning Iraqi journalist entered the country from Tunisia and was last in touch with the paper through a third party on Sunday, when he was on the outskirts of Zawiya, which saw heavy fighting in recent days.
The office of French President Nicolas Sarkozy said Paris regarded the NLC as Libya's "legitimate representative".
Mustafa Gheriani, a representative for the rebels in their eastern stronghold of Benghazi, said he expected other EU members to follow suit.
But a spokesman for the EU foreign affairs chief, Baroness Ashton, said: "We cannot unilaterally rush into recognising groups."
The foreign ministers of Italy and Spain emphasised the need for the EU to act with one voice.
"Italy wants a European decision that everyone shares unanimously because that's how we act credibly," Italy's Franco Frattini said.
Spain's Trinidad Jimenez said: "The possibility of this recognition must be the result of agreement among all of the countries of the European Union."
President Sarkozy's decision did find support in the European Parliament where MEPs adopted a resolution calling on the EU as a whole to recognise formally Libya's opposition as the only legitimate authority.
After meeting Nato defence ministers in Brussels, Secretary General Anders Fogh Rasmussen said the alliance planned to move more ships to the Mediterranean but more discussion was needed on a possible no-fly zone.
"We considered... initial options regarding a possible no-fly zone in case Nato were to receive a clear UN mandate," he said.
"Ministers agreed that further planning will be required."
Saif al-Islam Gaddafi, the Libyan leader's most prominent son, said the three-strong crew of a Dutch navy helicopter who were captured on 27 February during a botched evacuation mission near Sirte would be released but their helicopter would stay in Libya.
"Today we are going to hand over the Dutch soldiers to the Maltese and Greeks," he told Reuters news agency on Thursday.
"We told them, don't come back again without our permission. We captured the first Nato soldiers, we are sending them back home. But we are still keeping their helicopter."
Dutch defence and foreign ministry officials could not immediately comment.
Over the past few days, top officials from the Dutch government travelled to the Mediterranean and held secret negotiations with Col Gaddafi's government on freeing the crew, Radio Netherlands Worldwide reports.
The Dutch ambassador to Libya recently visited the crew and reported that they were in good condition.